Support for multiarch so dependencies

This pull request makes multiple so dependencies with different classifiers work correctly. So, you could have a dependency with classifier=armeabi, and the same dependency with classifier=x86 in the same project.

There are two major changes:

1. We drop duplicate library names when generating LOCAL_STATIC_LIBRARIES and LOCAL_SHARED_LIBRARIES
2. We ignore native libs that do not match current TARGET_ARCH_ABI

These two changes should guarantee that correct libraries will be used when APP_ABI is set in Application.mk to contain multiple entries.

**Note! Multiarch apklibs are not 100% working yet, but these changes should not break any existing functionality**